Flexible time-frequency multiplexing structure for wireless communication

ABSTRACT

Techniques for efficiently sending data in a wireless communication system are described. Code division multiplexing (CDM) or orthogonal frequency division multiplexing (OFDM) may be selected for each traffic segment, which may correspond to specific time frequency resources. An output waveform comprised of traffic and overhead segments may be generated. Each traffic segment may carry CDM data at a chip rate if CDM is selected or OFDM data if OFDM is selected. OFDM symbols may be generated at a sample rate that may be an integer ratio of the chip rate and may have a duration that may be determined based on the traffic segment duration. The output waveform may carry CDM data and/or OFDM data on subcarriers corresponding to at least one carrier in a spectral allocation and may further carry OFDM data on remaining usable subcarriers in the spectral allocation.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present application for patent is a continuation application of andclaims priority to patent application Ser. No. 11/676,939, entitled,“Flexible Time-Frequency Multiplexing Structure For WirelessCommunication”, filed on Feb. 20, 2007, and also claims priority toProvisional Application Ser. No. 60/775,443, entitled “WirelessCommunication System and Method,” and Provisional Application Ser. No.60/775,693, entitled “DO Communication System and Method,” both filedFeb. 21, 2006, assigned to the assignee hereof, and expresslyincorporated herein by reference.

BACKGROUND

I. Field

The present disclosure relates generally to communication, and morespecifically to transmission techniques for a wireless communicationsystem.

II. Background

Wireless communication systems are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These systems may be multiple-access systems capable ofsupporting multiple users by sharing the available system resources.Examples of such multiple-access systems include Code Division MultipleAccess (CDMA) systems, Time Division Multiple Access (TDMA) systems,Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA(OFDMA) systems, and Single-Carrier FDMA (SC-FDMA) systems.

A multiple-access system may utilize one or more multiplexing schemessuch as code division multiplexing (CDM), time division multiplexing(TDM), etc. The system may be deployed and may serve existing terminals.It may be desirable to improve the performance of the system whileretaining backward compatibility for the existing terminals. Forexample, it may be desirable to employ spatial techniques such asmultiple-input multiple-output (MIMO) and spatial division multipleaccess (SDMA) to improve throughput and/or reliability by exploitingadditional spatial dimensionalities provided by use of multipleantennas.

There is therefore a need in the art for transmission techniques thatcan support advanced communication techniques (e.g., spatial techniques)and improve bandwidth utilization while retaining backward compatibilityfor existing terminals.

SUMMARY

Techniques for efficiently sending and receiving data in a wirelesscommunication system are described herein. The techniques utilize a slotstructure that is backward compatible with existing design. Thetechniques also selectively employ orthogonal frequency divisionmultiplexing (OFDM) to efficiently support spatial techniques and/orother advanced communication techniques.

According to an aspect, an apparatus is described which selects CDM orOFDM for each of at least one traffic segment. Each traffic segment maycorrespond to specific time frequency resources. The apparatus generatesan output waveform comprised of the at least one traffic segment, witheach traffic segment carrying CDM data if CDM is selected for thetraffic segment or OFDM data if OFDM is selected for the trafficsegment. CDM data is data processed based on CDM, e.g., channelized withdifferent orthogonal codes. OFDM data is data processed based on OFDM,e.g., sent on multiple subcarriers in the frequency domain.

According to another aspect, an apparatus is described which selects CDMor OFDM for a traffic interval, generates CDM data at a chip rate andsends the CDM data in the traffic interval if CDM is selected, andgenerates at least one OFDM symbol at a sample rate and sends the atleast one OFDM symbol in the traffic interval if OFDM is selected. Thesample rate is related to the chip rate by an integer ratio. Each OFDMsymbol has a duration determined based on the duration of the trafficinterval.

According to yet another aspect, an apparatus is described whichdetermines a first set of subcarriers corresponding to at least onecarrier in a spectral allocation and also determines a second set ofsubcarriers corresponding to remaining usable subcarriers in thespectral allocation. The apparatus generates an output waveformcomprising CDM data or OFDM data or both CDM data and OFDM data on thefirst set of subcarriers and further comprising OFDM data on the secondset of subcarriers.

According to yet another aspect, an apparatus is described whichgenerates a first set of at least one OFDM symbol in accordance with afirst OFDM symbol numerology for a first terminal and generates a secondset of at least one OFDM symbol in accordance with a second OFDM symbolnumerology for a second terminal The first and second OFDM symbolnumerologies may be associated with different OFDM symbol durations,different numbers of subcarriers, different cyclic prefix lengths, etc.

According to yet another aspect, an apparatus is described whichdetermines whether CDM or OFDM is used for a traffic segment, processesreceived samples to recover CDM data sent in the traffic segment if CDMis used, and processes the received samples to recover OFDM data sent inthe traffic segment if OFDM is used.

Various aspects and features of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a High Rate Packet Data (HRPD) communication system.

FIG. 2 shows a single-carrier slot structure that supports CDM.

FIG. 3A shows a single-carrier slot structure that supports OFDM.

FIG. 3B shows a single-carrier slot structure that supports CDM andOFDM.

FIG. 4 shows a multi-carrier slot structure that supports CDM.

FIG. 5 shows a multi-carrier slot structure that supports CDM and OFDM.

FIG. 6 shows another multi-carrier slot structure that supports CDM andOFDM.

FIG. 7 shows a slot structure that supports OFDM and CDM.

FIG. 8 shows a slot structure that supports OFDM in a 5 MHz spectralallocation.

FIG. 9 shows a block diagram of an access point and a terminal.

FIG. 10 shows a design of a transmit (TX) CDM/OFDM processor.

FIG. 11 shows another design of a TX CDM/OFDM processor.

FIG. 12 shows a design of a receive (RX) CDM/OFDM processor.

FIG. 13 shows another design of an RX CDM/OFDM processor.

FIG. 14 shows a process for sending data with selectable CDM and OFDM.

FIG. 15 shows a process for sending data with suitable OFDM symbolnumerology.

FIG. 16 shows a process for efficiently sending data using availableresources.

FIG. 17 shows a process for sending data with multiple OFDM symbolnumerologies.

FIG. 18 shows a process for receiving data sent with CDM or OFDM.

DETAILED DESCRIPTION

The transmission techniques described herein may be used for variouswireless communication systems such as CDMA, TDMA, FDMA, OFDMA, andSC-FDMA systems. The terms “systems” and “networks” are often usedinterchangeably. A CDMA system may implement a radio technology suchcdma2000, Universal Terrestrial Radio Access (UTRA), Evolved UTRA(E-UTRA), etc. cdma2000 covers IS-2000, IS-95 and IS-856 standards. UTRAincludes Wideband-CDMA (W-CDMA) and Low Chip Rate (LCR). A TDMA systemmay implement a radio technology such as Global System for MobileCommunications (GSM). An OFDMA system may implement a radio technologysuch as Long Term Evolution (LTE) (which is part of E-UTRA), IEEE802.20, Flash-OFDM®, etc. UTRA, E-UTRA, GSM and LTE are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 is described in documents from an organizationnamed “3rd Generation Partnership Project 2” (3GPP2). These variousradio technologies and standards are known in the art.

The techniques may be used to support MIMO, SDMA, and other advancedcommunication techniques. For MIMO and SDMA, both inter-symbolinterference due to multipath and spatial (or inter-layer) interferencedue to simultaneous transmission of multiple data streams should beaddressed in order to maximize signal-to-noise-and-interference ratio(SINR) and link throughput. OFDM is better suited than CDM for spatialtechniques such as MIMO and SDMA because OFDM provides a simplemechanism to combat inter-symbol interference. By using OFDM, aMIMO/SDMA design may just address spatial interference. Hence, it isdesirable to replace CDMA waveform components with OFDM waveformcomponents whenever spatial techniques such as MIMO and SDMA areemployed. The available spectrum may also be better utilized with OFDM,as compared with multi-carrier CDMA, whenever the available spectrum(excluding the guard band) is not an integer multiple of the bandwidthof a single-carrier CDMA waveform.

For clarity, various aspects of the techniques are described below for aHigh Rate Packet Data (HRPD) system that implements IS-856. HRPD is alsoreferred to as Evolution-Data Optimized (EV-DO), Data Optimized (DO),High Data Rate (HDR), etc. The terms HRPD and EV-DO are often usedinterchangeably. Currently, HRPD Revisions (Revs.) 0, A, and B have beenstandardized, HRPD Revs. 0 and A are deployed, and HRPD Rev. C is underdevelopment. HRPD Revs. 0 and A cover single-carrier HRPD (1xHRPD). HRPDRev. B covers multi-carrier HRPD and is backward compatible with HRPDRevs. 0 and A. The techniques described herein may be incorporated inany HRPD revision. For clarity, HRPD terminology is used in much of thedescription below.

FIG. 1 shows an HRPD communication system 100 with multiple accesspoints 110 and multiple terminals 120. An access point is generally afixed station that communicates with the terminals and may also bereferred to as a base station, a Node B, etc. Each access point 110provides communication coverage for a particular geographic area andsupports communication for the terminals located within the coveragearea. Access points 110 may couple to a system controller 130 thatprovides coordination and control for these access points. Systemcontroller 130 may include network entities such as a Base StationController (BSC), a Packet Control Function (PCF), a Packet Data ServingNode (PDSN), etc.

Terminals 120 may be dispersed throughout the system, and each terminalmay be stationary or mobile. A terminal may also be referred to as anaccess terminal, a mobile station, a user equipment, a subscriber unit,a station, etc. A terminal may be a cellular phone, a personal digitalassistant (PDA), a wireless device, a handheld device, a wireless modem,a laptop computer, etc. A terminal may support any HRPD Revision. InHRPD, a terminal may receive a transmission on the forward link from oneaccess point at any given moment and may send a transmission on thereverse link to one or more access points. The forward link (ordownlink) refers to the communication link from the access points to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the access points.

FIG. 2 shows a single-carrier slot structure 200 that supports CDM onthe forward link in HRPD. The transmission timeline is partitioned intoslots. Each slot has a duration of 1.667 milliseconds (ms) and spans2048 chips. Each chip has a duration of 813.8 nanoseconds (ns) for achip rate of 1.2288 mega chips/second (Mcps). Each slot is divided intotwo identical half-slots. Each half-slot includes (i) an overheadsegment composed of a pilot segment at the center of the half-slot andtwo Media Access Control (MAC) segments on both sides of the pilotsegment and (ii) two traffic segments on both sides of the overheadsegment. The traffic segments may also be referred to as traffic channelsegments, data segments, data fields, etc. The pilot segment carriespilot and has a duration of 96 chips. Each MAC segment carries signaling(e.g., reverse power control (RPC) information) and has a duration of 64chips. Each traffic segment carries traffic data (e.g., unicast data forspecific terminals, broadcast data, etc.) and has a duration of 400chips.

HRPD Revs. 0, A and B use CDM for data sent in the traffic segments. Atraffic segment may carry CDM data for one or more terminals beingserved by an access point. The traffic data for each terminal may beprocessed based on coding and modulation parameters determined bychannel feedback received from that terminal to generate data symbols.The data symbols for the one or more terminals may be demultiplexed andcovered with 16-chip Walsh functions or codes to generate the CDM datafor the traffic segment. The CDM data is thus generated in the timedomain using Walsh functions. A CDM traffic segment is a traffic segmentcarrying CDM data.

It may be desirable to use OFDM and/or single-carrier frequency divisionmultiplexing (SC-FDM) for data sent in the traffic segments. OFDM andSC-FDM partition the available bandwidth into multiple orthogonalsubcarriers, which are also referred to as tones, bins, etc. Eachsubcarrier may be modulated with data. In general, modulation symbolsare sent in the frequency domain with OFDM and in the time domain withSC-FDM. OFDM and SC-FDM have certain desirable characteristics such asthe ability to readily combat intersymbol interference (ISI) caused byfrequency selective fading. OFDM can also efficiently support MIMO andSDMA, which may be applied independently on each subcarrier and may thusprovide good performance in a frequency selective channel. For clarity,the use of OFDM to send data is described below.

It may be desirable to support OFDM while retaining backwardcompatibility with HRPD Revs. 0, A and B. In HRPD, the pilot and MACsegments may be demodulated by all active terminals at all times whereasthe traffic segments may be demodulated by only the terminals beingserved. Hence, backward compatibility may be achieved by retaining thepilot and MAC segments and modifying the traffic segments. OFDM data maybe sent in an HRPD waveform by replacing the CDM data in a given400-chip traffic segment with one or more OFDM symbols having a totalduration of 400 chips or less.

FIG. 3A shows a single-carrier slot structure 300 that supports OFDM inHRPD. For simplicity, only one half-slot is shown in FIG. 3A. Thehalf-slot includes (i) an overhead segment composed of a 96-chip pilotsegment at the center of the half-slot and two 64-chip MAC segments onboth sides of the pilot segment and (ii) two traffic segments on bothsides of the overhead segment. In general, each traffic segment maycarry one or more OFDM symbols. In the example shown in FIG. 3A, eachtraffic segment carries two OFDM symbols, and each OFDM symbol has aduration of 200 chips and is sent in one OFDM symbol period of 200chips.

FIG. 3B shows a single-carrier slot structure 302 that supports CDM andOFDM in HRPD. A half-slot includes (i) an overhead segment composed of a96-chip pilot segment and two 64-chip MAC segments and (ii) two trafficsegments on both sides of the overhead segment. In one design, CDM orOFDM may be selected for each traffic segment. In this design, eachtraffic segment may carry CDM data if CDM is selected or one or moreOFDM symbols if OFDM is selected. In other design, a traffic segment maycarry both CDM data and OFDM data. For example, a traffic segment maycarry CDM data in half of the traffic segment and one or more OFDMsymbols in the other half of the traffic segment.

In general, OFDM symbols may be generated based on various OFDM symbolnumerologies or designs. Each OFDM symbol numerology is associated withspecific values for pertinent parameters such as OFDM symbol duration,number of subcarriers, cyclic prefix length, etc. The OFDM symbolduration should be an integer divisor of the 400-chip traffic segment inorder to fully utilize the traffic segment. Furthermore, the sample ratefor the OFDM symbols should be an integer multiple of the chip rate forthe CDM data in order to simplify processing at the access points andterminals.

Table 1 lists three example OFDM symbol numerologies for HRPD. Thesenumerologies are selected to be compatible with HRPD slot structure andchip rate so that (i) an integer number of OFDM symbols is sent in atraffic segment and (ii) the sample rate for the OFDM symbols is aninteger multiple of the chip rate for the CDM data. The numerologies arefurther selected such that the total number of subcarriers, whichdetermines a discrete Fourier transform (DFT) size, allow for efficientgeneration of the OFDM symbols. For these numerologies, the total numberof subcarriers is not a power of 2 but has small prime factors. Forexample, 90 subcarriers may be obtained with prime factors of 2, 3, 3and 5. The small prime factors may allow for efficient mixed-radix fastFourier transform (FFT) implementations to generate the OFDM symbols.The numerologies shown in Table 1 allow for efficient embedding of OFDMdata in an HRPD waveform.

TABLE 1 Normal Normal Normal OFDM Symbol OFDM Symbol OFDM SymbolParameter Numerology 1 Numerology 2 Numerology 3 Unit Sample rate 1.2288× n 1.2288 × n 1.2288 × n Msps Number of subcarriers    90 × n   180 × n  360 × n Subcarrier spacing 13.65333 . . . 6.82666 . . . 3.41333 . . .KHz Useful portion 90   180 360 chips (73.2421875 μs) (146.484375 μs)(292.96875 μs) Cyclic prefix length 7.5  16  36 chips    (≈6.10 μs)  (≈13.02 μs)   (≈29.30 μs) Guard time for 2.5  4  4 chips windowing   (≈2.03 μs)    (≈3.26 μs)   (≈3.26 μs) OFDM symbol 100    200 400chips duration   (≈81.38 μs)   (≈162.76 μs)  (≈325.52 μs)

Any of the OFDM symbol numerologies in Table 1 may be used to replaceCDM data with OFDM data in a traffic segment. These OFDM symbolnumerologies provide different tradeoffs with respect to Doppler spreadand multipath delay tolerance. Numerology 1 has the largest subcarrierspacing and the shortest cyclic prefix as compared to numerologies 2 and3. Hence, numerology 1 may provide better Doppler tolerance (due to thelarger subcarrier spacing) and may enable high spectral efficiency inhigh-speed vehicular channels at the expense of lower delay tolerance(due to the shorter cyclic prefix). Numerology 3 has the smallestsubcarrier spacing and the longest cyclic prefix as compared tonumerologies 1 and 2. Hence, numerology 3 may provide lower Dopplertolerance (due to the smaller subcarrier spacing) but higher delaytolerance (due to the longer cyclic prefix), which may enable highspectral efficiency in the presence of large multipath delays such asthose induced by repeaters.

Other OFDM symbol numerologies may also be used for the trafficsegments. In general, the OFDM symbol numerologies may be selected suchthat (i) the OFDM symbol duration and sample rate are compatible withthe HRPD slot format and chip rate, respectively, and (ii) the DFT sizeallows for efficient OFDM symbol generation. This may then allow forreplacement of CDM data in the HRPD forward link waveform with OFDM datain an efficient and backward compatible manner. CDM data may beselectively replaced with OFDM data in each traffic segment. Overheadsegments may be retained for backward compatibility.

In one design, a fixed OFDM symbol numerology is used for all trafficsegments carrying OFDM data. The terminals may know this OFDM symbolnumerology a priori and may be able to demodulate the OFDM data withoutany signaling on numerology.

In another design, configurable OFDM symbol numerology may be used for agiven traffic segment carrying OFDM data. A set of numerologies (e.g.,those listed in Table 1) may be supported. Different numerologies may beused for different terminals. A suitable numerology may be selected foreach terminal based on the channel conditions of that terminal. Forexample, numerology 1 may be used for a terminal traveling at highspeed, numerology 3 may be used for a terminal with large multipathdelay spread, and numerology 2 may be used for a terminal with moderatespeed and/or moderate multipath delay spread.

FIG. 4 shows a multi-carrier slot structure 400 that supports CDM inHRPD. In HRPD Rev. B, multiple 1xHRPD waveforms may be multiplexed inthe frequency domain to obtain a multi-carrier HRPD waveform that fillsa given spectral allocation. In the example show in FIG. 4, three 1xHRPDwaveforms for three HRPD carriers 1, 2 and 3 are frequency multiplexedin a 5 MHz spectral allocation. Each 1xHRPD waveform is generated for adifferent carrier and occupies approximately 1.25 MHz. The three 1xHRPDwaveforms occupy approximately 3×1.25=3.75 MHz, which may leaverelatively large guard bands at both edges of the 5 MHz spectralallocation. The spacing between adjacent carriers is not specified inHRPD but is typically selected to provide a small transition bandbetween adjacent 1xHRPD waveforms.

As shown in FIG. 4, the multi-carrier HRPD waveform includes threeoverhead segments and six traffic segments for the three carriers ineach half-slot. Each traffic segment may carry CDM data, as shown inFIG. 4. The CDM data in each traffic segment in the multi-carrier HRPDwaveform may be selectively replaced with OFDM data. Furthermore, thetraffic and overhead segments in the multi-carrier HRPD waveform may bearranged to efficiently utilize the spectral allocation.

FIG. 5 shows a multi-carrier slot structure 500 that supports CDM andOFDM in HRPD. In the example shown in FIG. 5, three HRPD carriers aresent in a 5 MHz spectral allocation and are spaced as close as possiblein order to improve bandwidth utilization. For each HRPD carrier, eachhalf-slot includes (i) an overhead segment composed of the pilot and MACsegments and (ii) two traffic segments on both sides of the overheadsegment. HRPD carrier 1 includes traffic segments (TS) 1 a and 1 b tothe left and right of the overhead segment, HRPD carrier 2 includestraffic segments 2 a and 2 b to the left and right of the overheadsegment, and HRPD carrier 3 includes traffic segments 3 a and 3 b to theleft and right of the overhead segment. Each traffic segment for eachHRPD carrier may carry CDM data or OFDM data.

It is customary to deploy at most three HRPD carriers (each spanningroughly 1.25 MHz) in a 5 MHz spectral allocation. It is not practical toaccommodate a fourth HRPD carrier in the 5 MHz spectral allocation,because this would leave too small a guard band between the HRPD systemand an incompatible system that may be deployed outside the 5 MHzallocation. On the other hand, with three HRPD carriers, only about 3.75MHz of the 5 MHz spectral allocation is actually utilized by the system,implying a guard band of roughly 1.25 MHz. This guard band size may betoo large in some cases, which means the multi-carrier system isinefficient in its usage of the available spectrum. This limitation maybe overcome by extending the techniques described above. For 3-carrierHRPD in 5 MHz spectral allocation, OFDM symbols may be generated at asample rate of 4×1.2288=4.9152 Mcps for n=4, as shown in FIG. 5. TheOFDM symbols may then occupy most of the 5 MHz spectral allocation.Alternatively, the OFDM symbols may be generated at a sample rate of3×1.2288=3.6864 Mcps for n=3, which is not shown in FIG. 5.

An OFDM symbol may be generated for each OFDM symbol period in a trafficinterval. Each OFDM symbol period is 200 chips with OFDM symbolnumerology 2 in Table 1. An OFDM symbol may carry OFDM data on (i)subcarriers corresponding to traffic segments used for OFDM and (ii)remaining usable subcarriers at both edges of the spectral allocation.The OFDM symbol may also be nulled out on subcarriers corresponding totraffic segments with CDM data. The OFDM symbol may thus carry OFDM datathat may selectively replace CDM data in zero or more traffic segmentsfor zero or more HRPD carriers. OFDM allows for better utilization ofthe available spectrum in the 5 MHz spectral allocation.

The spacing between HRPD carriers may be selected based on variousfactors such as a pulse shaping filter used for CDM, the manner in whichCDM data and/or OFDM data is generated, etc. Guard subcarriers, whichare subcarriers with no transmission, may be used at both edges of thespectral allocation. The number of guard subcarriers at the band edgesmay be selected based on spurious emission requirements and/or otherfactors.

FIG. 6 shows a multi-carrier slot structure 600 that supports CDM andOFDM in HRPD and more fully utilize the available bandwidth. Slotstructure 600 includes all of the traffic and overhead segments in slotstructure 500 in FIG. 5. Slot structure 600 further includes OFDM datain spectral portions that are not used for the pilot or MAC segments inthe 224-chip overhead interval.

Additional OFDM symbol numerologies may be defined for the 224-chipoverhead interval covering the pilot and MAC segments. Thesenumerologies may be selected such that (i) an integer number of OFDMsymbols may be sent in the overhead interval and (ii) the sample ratefor the OFDM symbols is an integer multiple of the chip rate. Table 2lists two example OFDM symbol numerologies for the overhead interval.The OFDM symbols sent in the overhead interval are referred to as “long”OFDM symbols because their durations are longer than the durations ofthe “normal” OFDM symbols sent in the traffic intervals with thecorresponding numerologies in Table 1.

TABLE 2 Long Long OFDM Symbol OFDM Symbol Parameter Numerology 1Numerology 2 Unit Sample rate 1.2288 × n 1.2288 × n Msps Number ofsubcarriers   100 × n   200 × n Subcarrier spacing 12.288 . . . 6.144 .. . KHz Useful portion 100  200 chips (≈81.38 μs) (≈162.76 μs) Cyclicprefix length 8  20 chips  (≈6.51 μs)  (≈16.28 μs) Guard time for 4  4chips windowing  (≈3.26 μs)  (≈3.26 μs) OFDM symbol 112  224 chipsduration (≈91.15 μs) (≈182.29 μs)

Other OFDM symbol numerologies may also be used for the overheadinterval. In general, the OFDM symbol numerologies may be selected suchthat (i) the OFDM symbol duration and sample rate are compatible withthe HRPD slot format and chip rate, respectively, and (ii) the DFT sizeallows for efficient OFDM symbol generation.

An OFDM symbol may be generated for each OFDM symbol period in theoverhead interval as described below. The OFDM symbol may carry OFDMdata in subcarriers corresponding to the portions of the bandwidth thatare not used for the pilot and MAC segments. The OFDM symbol may benulled out on subcarriers corresponding to the pilot and MAC segments.Overall spectral utilization may be improved by using one or more longOFDM symbols in the overhead interval.

In the designs shown in FIGS. 5 and 6, four logical channels Ch1, Ch2,Ch3 and Ch4 may be defined for the traffic segments. These logicalchannels may also be referred to as data channels, traffic channels,etc. Logical channel Ch1 may include traffic segments 1 a and 1 b senton HRPD carrier 1, logical channel Ch2 may include traffic segments 2 aand 2 b sent on HRPD carrier 2, logical channel Ch3 may include trafficsegments 3 a and 3 b sent on HRPD carrier 3, and logical channel Ch4 mayinclude traffic segments 4 a, 4 b and 4 c sent on the remaining usablespectrum. Logical channels Ch1, Ch2 and Ch3 thus correspond tosubcarriers that overlap with HRPD carriers 1, 2 and 3, respectively.Logical channels Ch1, Ch2 and Ch3 may switch between CDM and OFDM ineach slot, each half-slot, etc. Logical channel Ch4 has no associatedHRPD carrier and may be used to improve bandwidth utilization. Logicalchannel Ch4 may also be partitioned into two logical subchannels, e.g.,a lower Ch4 and an upper Ch4, with each logical subchannel including acontiguous set of subcarriers. The logical channels may be scheduledindependently. For example, each logical channel may be scheduled basedon channel quality feedback received from the terminals for that logicalchannel.

In general, any number of HRPD carriers may be sent in a given spectralallocation. For each HRPD carrier, each traffic segment may carry CDMdata or OFDM data. OFDM data may also be sent in remaining usablespectrum not used by the HRPD carriers.

FIG. 7 shows a slot structure 700 that supports OFDM and CDM for asingle HRPD carrier in a 5 MHz spectral allocation. In the example shownin FIG. 7, the single HRPD carrier is located near one edge of the 5 MHzspectral allocation. The pilot and MAC segments for the HRPD carrier aregenerated and sent in the center of the half-slot, as described above inFIGS. 2 through 6. Each traffic segment of the HRPD carrier may carryCDM data or OFDM data.

An OFDM spectrum may be defined to include all usable spectrum in thespectral allocation except for the HRPD carrier. In the example shown inFIG. 7, the OFDM spectrum includes the usable spectrum on both sides ofthe HRPD carrier. The normal and long OFDM symbols may be expanded andused to carry data in the OFDM spectrum. Traffic data, signaling andpilot may be sent in the OFDM spectrum in any manner, e.g., using anytechniques commonly used in systems employing just OFDM or OFDMA. Forexample, pilot and signaling may be sent in any manner on anysubcarriers and symbol periods. The available subcarriers and symbolperiods may also be allocated to any number of terminals, and data maybe sent to the scheduled terminals in any manner.

In the design shown in FIG. 7, two logical channels Ch1 and Ch2 aredefined. Logical channel Ch1 includes traffic segments 1 a and 1 b senton HRPD carrier 1, and logical channel Ch2 includes traffic segments 2 athrough 2 f sent on the OFDM spectrum. Logical channel Ch1 may switchbetween CDM and OFDM in each slot, each half-slot, etc. Logical channelCh2 is not bound to any HRPD carrier and may be operated in a pure OFDMmode to carry just OFDM data. Traffic data, signaling, and/or pilot maybe sent with OFDM in any manner on logical channel Ch2.

FIG. 8 shows an HRPD slot structure 800 that supports OFDM in a 5 MHzspectral allocation. In the example shown in FIG. 8, the spectralallocation contains no HRPD carrier. The normal and long OFDM symbolsmay be used to send data in the entire available spectrum, except forthe guard subbands at the band edges. Logical channel Ch1 may be definedto cover the entire usable spectrum. Logical channel Ch1 may be operatedas if it is for an OFDM/OFDMA system and may incorporate design elementsfrom other OFDM/OFDMA technologies such as Flash OFDM®, IEEE 802.20,LTE, etc. The time frequency resources in logical channel Ch1 may bepartitioned into traffic resources used for traffic data, signalingresources used for signaling, pilot resources used for pilot, etc. Thesignaling resources may be used to schedule terminals and to assigntraffic resources to the scheduled terminals. The signaling resourcesmay also be used to facilitate hybrid automatic retransmission (H-ARQ)feedback, power control, etc. Various structural elements and physicallayer features of Flash-OFDM®, IEEE 802.20, LTE and/or other OFDM/OFDMAsystems may be employed for logical channel Ch1.

FIG. 9 shows a block diagram of a design of an access point 110 and aterminal 120, which are one of the access points and terminals inFIG. 1. For simplicity, only processing units for transmission on theforward link are shown in FIG. 9.

At access point 110, a TX CDM/OFDM processor 920 receives and processestraffic data and signaling as described below and provides outputsamples. A transmitter (TMTR) 922 processes (e.g., converts to analog,amplifies, filters, and frequency upconverts) the output samples andgenerates a forward link signal, which is transmitted via an antenna924. At terminal 120, an antenna 952 receives the forward link signalfrom access point 110 and provides a received signal to a receiver(RCVR) 954. Receiver 954 processes (e.g., filters, amplifies, frequencydownconverts, and digitizes) the received signal and provides receivedsamples. An RX CDM/OFDM processor 960 processes the received samples ina manner complementary to the processing by TX CDM/OFDM processor 920,as described below, and provides decoded data and received signaling forterminal 120.

Controllers 930 and 970 direct the operation at access point 110 andterminal 120, respectively. Memories 932 and 972 store program codes anddata for access point 110 and terminal 120, respectively.

FIG. 10 shows a block diagram of a TX CDM/OFDM processor 920 a, which isone design of TX CDM/OFDM processor 920 in FIG. 1. Processor 920 aincludes (i) a CDM processor 1010 that generates a CDM waveform carryingCDM data and overhead data and (ii) an OFDM processor 1050 thatgenerates an OFDM waveform carrying OFDM data.

Within CDM processor 1010, an encoder/interleaver 1012 receives trafficdata to be sent using CDM, encodes the traffic data based on a codingscheme, and interleaves (or reorders) the coded data. A symbol mapper1014 maps the interleaved data to data symbols based on a modulationscheme. A demultiplexer (Demux) 1016 demultiplexes the data symbols intomultiple (e.g., 16) streams. A Walsh cover unit 1018 covers orchannelizes each data symbol stream with a different 16-chip Walsh codeto obtain a corresponding data chip stream. A summer 1020 sums multiple(e.g., 16) data chip streams for multiple Walsh codes and provides CDMdata at the chip rate. A TX overhead processor 1022 receives signalingfor the MAC segments and pilot data for the pilot segment and generatesoverhead data at the chip rate for the overhead segment. A TDMmultiplexer (Mux) 1024 receives the CDM data from summer 1020 and theoverhead data from processor 1022, provides the CDM data in trafficsegments carrying CDM data, and provides the overhead data in overheadsegments. A multiplier 1026 multiplies the output of TDM multiplexer1024 with a pseudo-noise (PN) sequence for the access point and providesoutput chips at the chip rate. A pulse shaping filter 1028 filters theoutput chips and provides a CDM waveform for one HRPD carrier. MultipleCDM waveforms for multiple HRPD carriers may be generated with multipleinstances of CDM processor 1010. These multiple CDM waveforms may beupconverted to the proper frequencies in the digital domain or theanalog domain.

Within OFDM processor 1050, an encoder/interleaver 1052 receives trafficdata to be sent using OFDM, encodes the traffic data based on a codingscheme, and interleaves the coded data. A symbol mapper 1054 maps theinterleaved data to data symbols. A symbol-to-subcarrier mapper 1056maps the data symbols to subcarriers used for OFDM. A zero insertionunit 1058 inserts zero symbols (which have signal value of zero) onsubcarriers not used for OFDM, e.g., subcarriers corresponding to CDMtraffic segments and overhead segments, null subcarriers, and guardsubcarriers. An inverse discrete Fourier transform (IDFT) unit 1060performs a K-point IDFT on the data symbols and zero symbols for K totalsubcarriers in each OFDM symbol period and provides a useful portioncontaining K time-domain samples. K is dependent on OFDM symbolnumerology and is given in Tables 1 and 2 for the normal and long OFDMsymbols. A cyclic prefix insertion unit 1062 copies the last C samplesof the useful portion and appends these C samples to the front of theuseful portion to form an OFDM symbol containing K+C samples at thesample rate. The sample rate may be n times the chip rate, where n maybe equal to 1, 2, 3, 4, etc. The repeated portion is referred to as acyclic prefix and is used to combat ISI caused by frequency selectivefading. A windowing/pulse shaping filter 1028 windows and filters thesamples from unit 1062 and provides an OFDM waveform. A summer 1070 sumsthe CDM waveform from CDM processor 1010 and the OFDM waveform from OFDMprocessor 1050 and provides an output waveform.

FIG. 11 shows a block diagram of a TX CDM/OFDM processor 920 b, which isanother design of TX CDM/OFDM processor 920 in FIG. 1. Processor 920 bmaps CDM data to subcarriers used for CDM and maps OFDM data tosubcarriers used for OFDM. Processor 920 b then generates an outputwaveform based on the mapped CDM data and OFDM data.

Within processor 920 b, a TX CDM processor 1110 receives and processestraffic data to be sent using CDM, signaling, and pilot and providesoutput chips. Processor 1110 may include units 1012 through 1026 in FIG.10. A DFT unit 1112 performs an L-point DFT on the output chips in eachOFDM symbol period and provides L frequency-domain symbols for Lsubcarriers. L is the number of subcarriers corresponding to an HRPDcarrier and may be dependent on the OFDM symbol numerology.

An encoder/interleaver 1120 and a symbol mapper 1122 process trafficdata to be sent using OFDM and provides data symbols. Asymbol-to-subcarrier mapper 1130 maps the frequency-domain symbols fromDFT unit 1112 to subcarriers used for CDM and further maps the datasymbols from symbol mapper 1122 to subcarriers used for OFDM. A zeroinsertion unit 1132 inserts zero symbols on subcarriers not used for CDMor OFDM, e.g., null and guard subcarriers. An IDFT unit 1134 performs aK-point IDFT on K symbols for each OFDM symbol period and provides auseful portion containing K time-domain samples. A cyclic prefixinsertion unit 1136 inserts a cyclic prefix to the useful portion andprovides an OFDM symbol containing K+C samples at the sample rate. Awindowing/pulse shaping filter 1138 windows and filters the samples fromunit 1136 and provides an output waveform. Filter 1136 may providesharper spectral roll-off than filter 1028 in FIG. 10, which may allowfor better utilization of the spectral allocation.

FIG. 12 shows a block diagram of an RX CDM/OFDM processor 960 a, whichis one design of RX CDM/OFDM processor 960 in FIG. 9. Processor 960 amay be used to receive the output waveform generated by TX CDM/OFDMprocessor 920 a in FIG. 10.

To recover CDM data, a filter 1212 obtains received samples fromreceiver 954, filters the received samples to remove spectral componentsoutside of an HRPD carrier of interest, performs conversion from samplerate to chip rate, and provides filtered chips. A multiplier 1214multiplies the filtered chips with the PN sequence used by the accesspoint and provides input chips. A TDM demultiplexer 1216 provides inputchips for the pilot segment to a channel estimator 1218, provides inputchips for the MAC segments to an RX overhead processor 1220, andprovides input chips for traffic segments carrying CDM data to a Walshdecover unit 1222. Channel estimator 1218 derives a channel estimatebased on the received pilot. Unit 1222 decovers or dechannelizes theinput samples for each Walsh code used for the CDM data and providesreceived symbols. A multiplexer 1224 multiplexes the received symbolsfor all Walsh codes. A data demodulator (Demod) 1226 performs coherentdetection on the received symbols with the channel estimate and providesdata symbol estimates, which are estimates of the data symbols sent withCDM. A deinterleaver/decoder 1228 deinterleaves and decodes the datasymbol estimates and provides decoded data for CDM. RX overheadprocessor 1220 processes the input chips for the MAC segments andprovides received signaling.

To recover OFDM data, a cyclic prefix removal unit 1252 obtains K+Creceived samples in each OFDM symbol period, removes the cyclic prefix,and provides K received samples for the useful portion. A DFT unit 1254performs a K-point DFT on the K received samples and provides K receivedsymbols for the K total subcarriers. A symbol-to-subcarrier demapper1256 obtains the received symbols for the K total subcarriers, providesreceived data symbols for the subcarriers used for OFDM to a datademodulator 1258, and may provide received pilot symbols to channelestimator 1218. Data demodulator 1258 performs data detection (e.g.,matched filtering, equalization, etc.) on the received data symbols withthe channel estimate from channel estimator 1218 and provides datasymbol estimates, which are estimates of the data symbols sent withOFDM. A deinterleaver/decoder 1260 deinterleaves and decodes the datasymbol estimates and provides decoded data for OFDM.

FIG. 13 shows a block diagram of an RX CDM/OFDM processor 960 b, whichis another design of RX CDM/OFDM processor 960 in FIG. 9. Processor 960b may be used to receive the output waveform generated by TX CDM/OFDMprocessor 920 b in FIG. 11. Within processor 960 b, a cyclic prefixremoval unit 1312 obtains K+C received samples in each OFDM symbolperiod, removes the cyclic prefix, and provides K received samples forthe useful portion. A DFT unit 1314 performs a K-point DFT on the Kreceived samples and provides K received symbols for the K totalsubcarriers. A symbol-to-subcarrier demapper 1316 obtains the receivedsymbols for the K total subcarriers, provides received symbols forsubcarriers used for CDM to an IDFT unit 1320, and provides receivedsymbols for subcarriers used for OFDM to a data demodulator 1330.

To recover CDM data, IDFT unit 1320 performs an L-point IDFT on Lreceived symbols for subcarriers used for CDM in an OFDM symbol periodand provides L time-domain samples. An RX CDM processor 1322 processesthe time-domain samples and provides received signaling and decoded datafor CDM. Processor 1322 may include units 1214 through 1228 in FIG. 12.To recover OFDM data, data demodulator 1330 performs data detection thereceived symbols from demapper 1316 with a channel estimate and providesdata symbol estimates. A deinterleaver/decoder 1332 deinterleaves anddecodes the data symbol estimates and provides decoded data for OFDM.

For clarity, various aspects of the techniques have been specificallydescribed for forward link transmission with CDM and OFDM in an HRPDsystem. The techniques may also be used for other combinations ofmultiplexing schemes such as, e.g., CDM and SC-FDM, CDM and TDM andOFDM, TDM and OFDM, etc. The techniques may also be used for otherwireless communication systems and for both the forward and reverselinks.

FIG. 14 shows a process 1400 for sending data in traffic segments withselectable CDM and OFDM. CDM or OFDM may be selected for each of atleast one traffic segment (block 1412). Each traffic segment maycorrespond to specific time and frequency resources and may carry CDMdata or OFDM data for unicast data sent to one or more specificterminals. At least one overhead segment with overhead data may begenerated (block 1414). An output waveform comprised of the at least onetraffic segment and the at least one overhead segment may be generated,with each traffic segment carrying CDM data if CDM is selected for thetraffic segment or OFDM data if OFDM is selected for the traffic segment(block 1416).

For a single carrier, CDM or OFDM may be selected for each of first andsecond traffic segments in a half-slot. An output waveform comprised ofthe first and second traffic segments and an overhead segment may begenerated for the half-slot, e.g., as shown in FIG. 3B. For multiplecarriers, CDM or OFDM may be selected for each of multiple trafficsegments for the multiple carriers. Multiple overhead segments withoverhead data may also be generated for the multiple carriers. An outputwaveform comprised of the multiple traffic segments and the multipleoverhead segments for the multiple carriers may be generated, e.g., asshown in FIGS. 5 through 7.

For both single carrier and multiple carriers, the output waveform maybe generated based on (i) a first waveform comprised of traffic segmentscarrying CDM data and overhead segments carrying overhead data and (ii)a second waveform comprised of traffic segments carrying OFDM data,e.g., as shown in FIG. 10. Alternatively, CDM data may be mapped tosubcarriers used for traffic segments carrying CDM data, OFDM data maybe mapped to subcarriers used for traffic segments carrying OFDM data,and overhead data may be mapped to subcarriers used for overheadsegments. An output waveform may then be generated based on the mappedCDM data, OFDM data, and overhead data, e.g., as shown in FIG. 11.

FIG. 15 shows a process 1500 for sending data with CDM or OFDM based onsuitably selected OFDM symbol numerology. CDM or OFDM may be selectedfor a traffic interval, or a traffic segment in the traffic interval(block 1512). CDM data may be generated at a chip rate and sent in thetraffic interval if CDM is selected (block 1514). At least one OFDMsymbol may be generated at a sample rate and sent in the trafficinterval if OFDM is selected (block 1516). The sample rate may berelated to the chip rate by an integer ratio. Each OFDM symbol may havea duration that is determined based on the duration of the trafficinterval. Overhead data may be generated in accordance with CDM at thechip rate (block 1518). The overhead data may be sent in an overheadinterval, and the CDM data or the at least one OFDM symbol may be sentin the traffic interval using TDM (block 1520).

For HRPD, the CDM data may be generated at a chip rate of 1.2288 Mcps.The at least one OFDM symbol may be generated at a sample rate of1.2288×n Msps, where n is the integer ratio. The traffic interval mayspan 400 chips, and each OFDM symbol may have a duration of 400/m chips,where m is an integer divisor. Each OFDM symbol may cover K subcarriers,where K may be an integer that is not a power of two.

For the traffic interval, CDM data may be generated at the chip rate forat least one carrier in a spectral allocation, and at least one OFDMsymbol may be generated at the sample rate for remaining usablesubcarriers in the spectral allocation. For the overhead interval, atleast one long OFDM symbol may be generated at the sample rate and mayhave a duration that is determined based on the duration of the overheadinterval, e.g., as shown in FIGS. 6 and 7.

FIG. 16 shows a process 1600 for efficiently sending data using theavailable time frequency resources. A first set of subcarrierscorresponding to at least one carrier in a spectral allocation may bedetermined (block 1612). A second set of subcarriers corresponding toremaining usable subcarriers in the spectral allocation may also bedetermined (block 1614). If multiple carriers are present, then atransition band may be provided between adjacent carriers and may bedetermined based on a transition edge of a pulse shaping filter used togenerate CDM data. The first set may exclude null subcarriers betweencarriers carrying different types of data. The first and second sets mayexclude guard subcarriers.

An output waveform comprising CDM data or OFDM data or both CDM data andOFDM data on the first set of subcarriers and further comprising OFDMdata on the second set of subcarriers may be generated (block 1616). Theoutput waveform may comprise CDM data or OFDM data on subcarrierscorresponding to each carrier. The output waveform may further compriseoverhead data for the at least one carrier and OFDM data on a third setof subcarriers in an overhead interval. The third set may containremaining usable subcarriers in the overhead interval.

FIG. 17 shows a process 1700 for sending data with dynamicallyselectable OFDM symbol numerologies. A first set of at least one OFDMsymbol may be generated in accordance with a first OFDM symbolnumerology for a first terminal (block 1712). A second set of at leastone OFDM symbol may be generated in accordance with a second OFDM symbolnumerology for a second terminal (block 1714). The first and second OFDMsymbol numerologies may be associated with different OFDM symboldurations, different numbers of subcarriers, different cyclic prefixlengths, etc. Overhead data may be generated in accordance with CDM(block 1716). The first set of at least one OFDM symbol may be sent in afirst time interval, the second set of at least one OFDM symbol may besent in a second time interval, and the overhead data may be sent in athird interval using TDM (block 1718).

FIG. 18 shows a process 1800 for receiving data sent with CDM or OFDM. Adetermination may be made whether CDM or OFDM is used for a trafficsegment (block 1812). Received samples may be processed to recover CDMdata sent in the traffic segment if CDM is used (block 1814). Thereceived samples may be processed to recover OFDM data sent in thetraffic segment if OFDM is used (block 1816). The received samples mayalso be processed to recover overhead data in an overhead segment thatis TDMed with the traffic segment (block 1818).

To recover OFDM data, the received samples may be processed (e.g.,cyclic prefix removed, inverse transformed, and demapped) to obtainreceived symbols for subcarriers used for the traffic segment. Thereceived symbols may then be processed (e.g., demodulated,deinterleaved, and decoded) to recover the OFDM data sent in the trafficsegment, e.g., as shown in FIG. 12 or 13. The OFDM data may also berecovered in other manners.

To recover CDM data, the received samples may be filtered to obtainfiltered samples for subcarriers used for the traffic segment. Thefiltered samples may be processed (e.g., descrambled) to obtain inputsamples for the traffic segment. The input samples may be decovered withmultiple orthogonal codes (e.g., Walsh codes) to obtain receivedsymbols. The received symbols may then be processed (e.g., demodulated,deinterleaved, and decoded) to recover the CDM data sent in the trafficsegment, as shown in FIG. 12. Alternatively, the received samples may beprocessed (e.g., cyclic prefix removed, inverse transformed, anddemapped) to obtain frequency-domain symbols for a plurality ofsubcarriers. Frequency-domain symbols for subcarriers used for thetraffic segment may be processed (e.g., transformed) to obtaintime-domain samples. The time-domain samples may be decovered withmultiple orthogonal codes to obtain received symbols. The receivedsymbols may then be processed (e.g., demodulated, deinterleaved, anddecoded) to recover the CDM data sent in the traffic segment, e.g., asshown in FIG. 13. The CDM data may also be recovered in other manners.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples described herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A method within an apparatus, comprising:determining a first set of subcarriers corresponding to at least onecarrier in a spectral allocation; determining a second set ofsubcarriers corresponding to remaining usable subcarriers in thespectral allocation; and generating an output waveform for simultaneoustransmission comprising mixed code division multiplexing (CDM) data andorthogonal frequency division multiplexing (OFDM) data on the first setof subcarriers, OFDM data on the second set of subcarriers and OFDM dataon a third set of subcarriers in an overhead interval, wherein ahalf-slot in a carrier of the at least one carrier comprises at leasttwo traffic segments, and wherein a first segment of the at least twotraffic segments comprises CDM data and a second segment of the at leasttwo traffic segments comprises OFDM data, wherein generating the outputwaveform further comprises generating overhead data for the third set ofsubcarriers in the overhead interval.
 2. An apparatus comprising: atleast one processor configured to determine a first set of subcarrierscorresponding to at least one carrier in a spectral allocation, todetermine a second set of subcarriers corresponding to remaining usablesubcarriers in the spectral allocation, and to generate an outputwaveform for simultaneous transmission comprising mixed code divisionmultiplexing (CDM) data and orthogonal frequency division multiplexing(OFDM) data on the first set of subcarriers, OFDM data on the second setof subcarriers and OFDM data on a third set of subcarriers in anoverhead interval, wherein a half-slot in a carrier of the at least onecarrier comprises at least two traffic segments, and wherein a firstsegment of the at least two traffic segments comprises CDM data and asecond segment of the at least two traffic segments comprises OFDM data,wherein the at least one processor generates overhead data for third setof subcarriers in the overhead interval; and a memory coupled to the atleast one processor.
 3. The apparatus of claim 2, wherein the at leastone processor determines the third set of subcarriers corresponding toremaining usable subcarriers in the overhead interval.
 4. The apparatusof claim 2, wherein the at least one carrier comprises multiplecarriers, and wherein the at least one processor generates the outputwaveform comprising CDM data or OFDM data on subcarriers correspondingto each of the multiple carriers and further comprising OFDM data on thesecond set of subcarriers.
 5. The apparatus of claim 4, wherein the atleast one processor determines at least one null subcarrier between acarrier with CDM data and an adjacent carrier with OFDM data, andwherein the first set of subcarriers excludes null subcarriers betweenthe multiple carriers.
 6. An apparatus comprising: means for determininga first set of subcarriers corresponding to at least one carrier in aspectral allocation; means for determining a second set of subcarrierscorresponding to remaining usable subcarriers in the spectralallocation; and means for generating an output waveform for simultaneoustransmission comprising mixed code division multiplexing (CDM) data andorthogonal frequency division multiplexing (OFDM) data on the first setof subcarriers, OFDM data on the second set of subcarriers and OFDM dataon a third set of subcarriers in an overhead interval, wherein ahalf-slot in a carrier of the at least one carrier comprises at leasttwo traffic segments, and wherein a first segment of the at least twotraffic segments comprises CDM data and a second segment of the at leasttwo traffic segments comprises OFDM data, wherein the means forgenerating the output waveform further comprises means for generatingoverhead data for the third set of subcarriers in the overhead interval.7. A method for wireless communication in a communication system, themethod comprising: determining a first set of subcarriers correspondingto at least one carrier in a spectral allocation; determining a secondset of subcarriers corresponding to remaining usable subcarriers in thespectral allocation; and generating an output waveform for simultaneoustransmission comprising mixed code division multiplexing (CDM) data andfrequency division multiplexing access data on the first set ofsubcarriers, frequency division multiplexing access data on at least onesubcarrier of the second set of subcarriers and frequency divisionmultiplexing access data on at least one subcarrier of a third set ofsubcarriers in an overhead interval, wherein a half-slot in a carrier ofthe at least one carrier comprises at least two traffic segments, andwherein a first segment of the at least two traffic segments comprisesCDM data and a second segment of the at least two traffic segmentscomprises frequency division multiplexing access data, whereingenerating the output waveform further comprises generating overheaddata for the at least one subcarrier of the third set of subcarriers inthe overhead interval.
 8. The method as defined in claim 7, wherein thefrequency division multiplexing access data is one or more of OrthogonalFrequency Division Multiplexing Access (OFDMA) data and Single CarrierFrequency Division Multiplexing Access (SC-FDMA) data.
 9. The method asdefined in claim 7, wherein the communication system is at least one ofa Long Term Evolution (LTE), LTE Advanced, Universal Terrestrial RadioAccess (UTRA), or Evolved UTRA (E-UTRA).
 10. The method as defined inclaim 7, further comprising determining the at least one subcarrier ofthe third set of subcarriers that corresponds to at least one remainingusable subcarrier in the overhead internal.
 11. The method as defined inclaim 7, further comprising determining at least one null subcarrierbetween a carrier with CDM data and an adjacent carrier with frequencydivision multiplexed access data, and wherein the first set ofsubcarriers excludes the at least one determined null subcarrier.
 12. Anapparatus for wireless communication in a communication system, theapparatus comprising: at least one processor configured to determine afirst set of subcarriers corresponding to at least one carrier in aspectral allocation; determine a second set of subcarriers correspondingto remaining usable subcarriers in the spectral allocation; and generatean output waveform for simultaneous transmission comprising mixed codedivision multiplexing (CDM) data and frequency division multiplexingaccess data on the first set of subcarriers, frequency divisionmultiplexing access data on at least one subcarrier of the second set ofsubcarriers and frequency division multiplexing access data on at leastone subcarrier of a third set of subcarriers in an overhead interval,wherein a half-slot in a carrier of the at least one carrier comprisesat least two traffic segments, and wherein a first segment of the atleast two traffic segments comprises CDM data and a second segment ofthe at least two traffic segments comprises frequency divisionmultiplexing access data, wherein generating the output waveform furthercomprises generating overhead data for the at least one subcarrier ofthe third set of subcarriers in the overhead interval.
 13. The apparatusas defined in claim 12, wherein the frequency division multiplexingaccess data is one or more of Orthogonal Frequency Division MultiplexingAccess (OFDMA) data and Single Carrier Frequency Division MultiplexingAccess (SC-FDMA) data.
 14. The apparatus as defined in claim 12, whereinthe communication system is at least one of a Long Term Evolution (LTE),LTE Advanced, Universal Terrestrial Radio Access (UTRA), or Evolved UTRA(E-UTRA).
 15. The apparatus as defined in claim 12, wherein the at leastone processor is further configured to determine the at least onesubcarrier of the third set of subcarriers that corresponds to at leastone remaining usable subcarrier in the overhead internal.
 16. Theapparatus as defined in claim 12, wherein the at least one processor isfurther configured to determine at least one null subcarrier between acarrier with CDM data and an adjacent carrier with frequency divisionmultiplexed access data, and wherein the first set of subcarriersexcludes the at least one determined null subcarrier.
 17. An apparatusfor use in a communication system, the apparatus comprising: means fordetermining a first set of subcarriers corresponding to at least onecarrier in a spectral allocation; means for determining a second set ofsubcarriers corresponding to remaining usable subcarriers in thespectral allocation; and means for generating an output waveform forsimultaneous transmission comprising mixed code division multiplexing(CDM) data and frequency division multiplexing access data on the firstset of subcarriers, frequency division multiplexing access data on atleast one subcarrier of the second set of subcarriers and frequencydivision multiplexing access data on at least one subcarrier of a thirdset of subcarriers in an overhead interval, wherein a half-slot in acarrier of the at least one carrier comprises at least two trafficsegments, and wherein a first segment of the at least two trafficsegments comprises CDM data and a second segment of the at least twotraffic segments comprises frequency division multiplexing access data,wherein generating the output waveform further comprises generatingoverhead data for the at least one subcarrier of the third set ofsubcarriers in the overhead interval.
 18. The apparatus as defined inclaim 17, wherein the frequency division multiplexing access data is oneor more of Orthogonal Frequency Division Multiplexing Access (OFDMA)data and Single Carrier Frequency Division Multiplexing Access (SC-FDMA)data.
 19. The apparatus as defined in claim 17, wherein thecommunication system is at least one of a Long Term Evolution (LTE), LTEAdvanced, Universal Terrestrial Radio Access (UTRA), or Evolved UTRA(E-UTRA).
 20. The apparatus as defined in claim 17, further comprisingmeans for determining the at least one subcarrier of the third set ofsubcarriers that corresponds to at least one remaining usable subcarrierin the overhead internal.
 21. The apparatus as defined in claim 17,further comprising means for determining at least one null subcarrierbetween a carrier with CDM data and an adjacent carrier with frequencydivision multiplexed access data, and wherein the first set ofsubcarriers excludes the at least one determined null subcarrier.
 22. Acomputer program product, comprising: a non-transitory computer-readablemedium comprising: code for causing a computer to determine a first setof subcarriers corresponding to at least one carrier in a spectralallocation; code for causing a computer to determine a second set ofsubcarriers corresponding to remaining usable subcarriers in thespectral allocation; and code for causing a computer to generate anoutput waveform for simultaneous transmission comprising mixed codedivision multiplexing (CDM) data and frequency division multiplexingaccess data on the first set of subcarriers, frequency divisionmultiplexing access data on at least one subcarrier of the second set ofsubcarriers and frequency division multiplexing access data on at leastone subcarrier of a third set of subcarriers in an overhead interval,wherein a half-slot in a carrier of the at least one carrier comprisesat least two traffic segments, and wherein a first segment of the atleast two traffic segments comprises CDM data and a second segment ofthe at least two traffic segments comprises frequency divisionmultiplexing access data, wherein generating the output waveform furthercomprises generating overhead data for the at least one subcarrier ofthe third set of subcarriers in the overhead interval.
 23. The computerprogram product as defined in claim 22, wherein the frequency divisionmultiplexing access data is one or more of Orthogonal Frequency DivisionMultiplexing Access (OFDMA) data and Single Carrier Frequency DivisionMultiplexing Access (SC-FDMA) data.
 24. The computer program product asdefined in claim 22, wherein the communication system is at least one ofa Long Term Evolution (LTE), LTE Advanced, Universal Terrestrial RadioAccess (UTRA), or Evolved UTRA (E-UTRA).
 25. The computer programproduct as defined in claim 22, the computer-readable medium furthercomprising: code for causing a computer to determine the at least onesubcarrier of the third set of subcarriers that corresponds to at leastone remaining usable subcarrier in the overhead internal.
 26. Thecomputer program product as defined in claim 22, the computer-readablemedium further comprising: code for causing a computer to determine atleast one null subcarrier between a carrier with CDM data and anadjacent carrier with frequency division multiplexed access data, andwherein the first set of subcarriers excludes the at least onedetermined null subcarrier.